I'm runnin' Linux Mint 12 and didn't like the default theme. I liked Adwaita but certain elements had to be changed.

I kept the top panel black. I made the bottom panel solid black and removed transparency.

On the top panel, I changed the bottom line from grey to green.

I installed 'Mint Corner Ripple.' Just bang top left corner with mouse and you will like!

I changed volume slider color from blue to green.

I shortened the width slightly of the calendar pop up.

I removed the blue on/off switches for some nicer ones.

In Overview mode, the only thing I didn't like, and changed, was the search box. I made it look the same as when it is active.

On The bottom panel, I replaced the cog icon on the Menu to a Mint logo icon.

I changed the color of the 'Window Switcher' from grey to green on the right side of the panel.

I'm using Mint-X-F icons
http://gnome-look.org/content/show.php/Mint-X-Faenza+Folders+%28Mint-X-F%29?content=135238

Put 'Adwaita-Mint' in /home/.themes folder and put the extensions in the 'extensions' folder in /usr/share/gnome-shell/extensions. Make backups of your extensions if you have the same ones (just in case you want to change back later).

Enjoy!